1. Field of the Invention
The present invention relates to a component mounting apparatus which is applied to the mounting of an electronic component onto an electronic circuit substrate, and more particularly, to a nozzle drop prevention device, which is installed in a mounting head equipped with a nozzle for picking up a component.
2. Description of Related Art
With the propagation of leadless electronic components (chip component) in recent years, the shape and size of components have been diversified, and in an electronic component mounting apparatus for mounting these electronic components, there have been demands for high-speed operation, high precision, high productivity, and high reliability.
A conventional electronic component mounting apparatus will be hereinafter described with reference to FIG. 7. In FIG. 7, the electronic component mounting apparatus comprises a mounting head 51 equipped with a nozzle for picking up an electronic component, a suction device 52 for attracting the electronic component with the nozzle, an XY robot 53 for moving the mounting head 51 in the X and Y directions, and a control device 54 which controls actions of the mounting head 51, the suction device 52, and the XY robot 53. It is noted that FIG. 7 shows only the main elements of the mounting head 51, and illustration of, for example, a body part is omitted.
Reference numeral 55 represents a spline shaft, to which two nuts 56, 57 are coupled such as to be movable in a direction of its axis. These nuts 56, 57 are supported in the body part (not shown) of the mounting head 51 via bearings 58, 59, respectively. By this construction, the spline shaft 55 is movable in the direction of its axis as well as rotatable around its axis, and it is driven to rotate by a motor 60 mounted on the mounting head 51 via a pulley 61, belt 62, and another pulley 63.
At the distal end 55a of the spline shaft 55 is mounted a nozzle 65 for picking up the electronic component 64. Inside the nozzle 65, a filter 66 is provided for preventing dust from entering into the nozzle when a suctional force is applied. The spline shaft 55 is pushed upwards by a compression spring 68 via a bearing 67 which is to be slidable in a circumferential direction, and by applying a pressing force from a voice coil motor 69, the spline shaft 55 or the nozzle 65 is lowered to perform pick up and mounting actions of the electronic component 64.
The actions of the component mounting apparatus with the above described construction will be explained. The control device 54 activates the XY robot 53 to move the mounting head 51 to a component pick-up position where the electronic component is picked up. Then, by the control of the control device 54, the voice coil motor 69 is driven so as to compress the compression spring 68, by which the nozzle 65 is lowered via the spline shaft 55, and at the same time the suction device 52 is driven so that the nozzle 65 picks up the electronic component 64 by suctional force. Next, the nozzle 65 is lifted by means of the voice coil motor 69. The XY robot 53 is then driven to move the mounting head 51 to a component mounting position above the circuit substrate, after which the nozzle 65 is lowered by means of the voice coil motor 69 so that the electronic component 64 is mounted on the circuit substrate. When the power source is off or at the time of a power failure, the pressing force is not applied from the voice coil motor 69, and thus the spline shaft 55 or nozzle 65 is prevented from dropping due to the force of the compression spring 68 which is pushing the bearing 67 upwards.
However, in the above described construction, since the spline shaft 55 is urged upwards by the force of the compression spring 68, the voice coil motor 69 needs to have a pressing force greater than the force of the compression spring 68, alone wherefore there is a problem that precise control of pressing force for the mounting purpose cannot be achieved. Also, the voice coil motor 69 needs to have a capacity greater than necessary, thus causing the size of the voice coil motor or the mounting head 51 to become bulky. Furthermore, in order for minimizing the change of the compression spring 68 due to compression, it is necessary to make enough room for the compression spring 68, whereby the mounting head 51 becomes elongated in a vertical direction.
In view of the above problems in the prior art, an object of the present invention is to provide a nozzle drop prevention device in a component mounting apparatus by which, without using a compression spring for pushing the nozzle upwards, the nozzle is prevented from falling when power is turned off or cut with a simple and compact construction, and by which a pressing force applied to the nozzle can be precisely controlled with a compact voice coil motor.
The nozzle drop prevention device according to the present invention is used in a component mounting apparatus including a mounting head in which a nozzle is disposed at a distal end of a shaft which is movable upwards and downwards for picking up and mounting a component, and comprises: a shaft driving means for driving the shaft upwards and downwards; a pair of first levers which is swingable in an open and a close directions and is forced in the close direction by a compression spring to hold the shaft in a gripping manner; a release pin for opening the first levers opposite the pivotally connected end by engaging with an open/close end of the first levers; a second lever for driving, the release pin toward the open/close end of the first levers; by a driving means and a tension spring for forcing the second lever in a reverse direction with respect to a direction in which the release pin is driven; wherein during an operation of the mounting head the shaft driving means is activated the first levers are opened via the second lever by driving the release pin, only after the shaft and at the end of the operation, the driving of the release pin by the second lever is released, so that the shaft is vertically supported by the first levers. Since the shaft can move upwards and downwards freely when the mounting head is in operation, pressure application control can be precisely made with a compact shaft driving means, and the nozzle can be prevented from dropping since the shaft is supported by the first lever at the end of the operation, and even when there is a power failure where controlling actions are not effectuated, nozzle drop can be prevented by the action of the spring, by which mechanical damages can be avoided and high reliability is realized.
Instead of providing a spring for forcing the second lever in a reverse direction with respect to a direction in which the release pin is driven, a reciprocating moving means for moving the second lever in a release pin driving direction and in a reverse direction with respect to the driving direction can be provided, with which, when the mounting head is in operation, only after the shaft driving means is activated are the first levers opened via the second lever by driving the release pin in driving direction and at the end of the operation, the driving of the release pin by the second lever is released, so that the shaft is vertically supported by the first levers. In this case, since the second lever is not forced by the spring in the direction opposite to the driving direction, the speed of response when the second lever is driven in the release pin driving direction is increased, i.e., the response of actions in both directions is enhanced, by which a high-speed mounting operation is realized. By employing a double-acting air cylinder device as the reciprocating moving means, high-speed operation of the second lever is possible by a simple construction with an air source and a solenoid valve.
In the case where the mounting head is equipped with a plurality of nozzles, the release pin is also provided in plurality so as to correspond to each of the nozzles, and the release pins are driven in synchronism by the second lever, by which a plurality of shafts can be collectively supported in a vertical direction and the nozzles can be prevented from dropping.
The component mounting method of the present invention, in which a component is picked up and mounted by a nozzle attached to a lower end of a shaft which is movable upwards and downwards, is characterized in that the shaft is kept fixed in a grasping manner, and only when a component is picked up or mounted is the grip of the shaft released, and the shaft is moved upwards and downwards by a vertical moving means. According to this method, since the shaft is freely movable when mounting a component, pressure application control can be precisely made with a compact vertical moving means.
Furthermore, the component mounting apparatus of the present invention comprises a shaft which is movable upwards and downwards; a nozzle mounted at a lower end of the shaft for carrying out component pick up and mounting operations; a gripping means for fixedly gripping the shaft at a predetermined position; a shaft driving means for moving the shaft upwards and downwards; and a grip release means for releasing the grip of the shaft by the gripping means only when picking up and mounting a component, by which the above method of mounting a component can be carried out and the above effects can be achieved.
By constructing a component mounting apparatus such that the gripping means comprises a pair of first levers pivotally connected at one end such that the first levers can swing in an open and close direction and is forced in the close direction by a spring to grip the shaft, and the grip release means comprises a release pin which causes the first levers to open by engaging releases grooves at an open/close end of the first levers and a means for driving the release pin toward the open/close end of the first levers only when picking up and mounting a component, the grip and the release of the grip of the shaft can be effected with a simple arrangement.